1. Field of the Invention
The invention relates to an inspection device for inspecting a sheet outputted by an image forming apparatus.
2. Description of Related Art
As an image forming apparatus which, when image disturbance is caused by the state of the interior of the image forming apparatus, does not continuedly print a faulty image, but can warn and at the same time, can stop a printing operation and can rapidly cope with the difficulty, there is known an apparatus proposed in Japanese Patent Application Laid-Open No. 5-318888. In this apparatus, the presence or absence of image disturbance on a sheet has been judged by comparing the image signal of an image formed on a photosensitive member and an image signal obtained by reading an image on a sheet after fixing with each other by a comparing circuit.
In this conventional method, however, the image signal of the image formed on the photosensitive member is the object of comparison and therefore, when it is compared with an image signal obtained after the intervention of a photosensitive member, a fixing portion and a solid state image sensor, there has been the possibility that even a normal sheet which is originally free of image disturbance is recognized as a faulty sheet.
Also, comparison has been made by transmitting the image signal of the image formed on the photosensitive member to the comparing circuit, reading the image on the sheet outputted from the image forming apparatus by the solid state image sensor, and transmitting the image signal of the image read by the solid state image sensor to the comparing circuit and therefore, communication of a great deal of image data has been effected. This also has led to the problem that a great load is applied to communication means.